Absorbent articles such as diapers, bandages, catamenials, and the like, generally comprise an absorbent core which is covered with some type of "topsheet" material which allows passage of body fluids from the skin area being contacted into the absorbent core. The purpose of the topsheet is partly sanitary and partly comfort for the wearer. For example, it is desirable to keep blood or other matter excreted from wounds away from the wound site. Accordingly, bandages typically have a topsheet designed for this purpose. Diaper topsheets are designed to allow urine to flow through and into the core, while giving the impression of skin dryness to the wearer.
Some of the earliest topsheet material was simply gauze; this was followed by various plastic-type materials; in recent years, formed-films of various types have been introduced. The objective with many of these topsheet materials is to allow rapid fluid passage through the topsheet material and into the absorbent core, while preventing re-flow of the fluid from the core back through the topsheet and back onto the skin (i.e., "re-wet").
A number of means have been suggested for improving topsheet material. For example, British Patent Specification No. 2,023,269, Dec. 28, 1979, discloses a disposable diaper comprising an air permeable topsheet to which is applied a surfactant to facilitate fluid passage therethrough. This surfactant is said to be preferably nonionic, and is uniformly impregnated into the topsheet. See also U.S. Pat. No. 3,967,623, issued July 6, 1976, which discloses a disposable absorbent pad having a perforated topsheet, and treated with surfactant to improve fluid flow.
U.S. Pat. No. 3,838,692, issued Oct. 1, 1974, discloses a sheet material suitable for use as a diaper topsheet which is generally hydrophobic in nature but which includes spaced hydrophilic passages to permit liquid to be transmitted through the sheet material. It appears that the preferred way to make this sheet material is by treating a hydrophilic nonwoven material with a hydrophobic composition, such as a rubber latex.
U.S. Pat. No. 3,929,135, issued Dec. 30, 1975, teaches a topsheet material for absorbent structures which is provided with tapered capillary holes to improve the transmission of body fluids to the absorbent core, without re-wet.
It is an object of the present invention to provide topsheet materials having improved fluid passage. It is another object of the invention to provide topsheet materials which have decreased re-wet. It is a further object of the invention to provide top-sheet materials which are prepared from otherwise hydrophobic polymers, but which are selectively rendered hydrophilic by surface modification, thereby improving fluid flow and re-wet performance. It is a further object of this invention to provide improved absorbent articles, such as bandages, diapers, catamenials, and the like, using said topsheet material. These and other objects are secured by the present invention, as will be seen by the following disclosure.